Flood potential depends on speed of spring thaw

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CHASKA HERALD

Those who study the weather have turned their eyes from winter storms to the temperatures of March and April.

The speed snow melts will determine the strength of what could be damaging floods.

All the factors are in place for the Minnesota River to overflow its banks.

The National Weather Service’s Feb. 27 Spring Flood Outlook looked at those factors. The good news, said NWS Hydrologist Craig Schmidt, is that the long-range forecast shows a gradual warm-up.

“All of the factors are in place for spring flooding to be a major threat,” Schmidt said. “And if we get extremely warm temperatures, or some heavy rainfall, we could have some major issues. If we end up with a very slow warm-up, slightly above normal later in March, then we could probably have a best-case scenario of snow melting a little bit each day and slowing down at night.”

The spring flood outlook factors are:

  • A wet autumn in 2018 left soil moisture above normal before the ground froze.
  • Snow pack, or the water level in the snow, is above normal, or significantly above normal, across the state.
  • There is a 2-4 foot frost depth over the region.

The Feb. 27 outlook at the Minnesota River gauge in Jordan showed an 80-90 percent chance of moderate flooding, with a 10-20 percent chance of major flooding. The Savage simulation showed a 75-85 percent chance of moderate flooding, and a 50-60 percent chance of major flooding.

“Everything is in place,” Schmidt said. “We have to see how it all plays out.”

The service’s next outlook will be updated March 9.

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